2024 Yes https://link.springer.com/article/10.1007/s11356-024-32843-8 Ongwandee, Maneerat Asia Exposure Study High School (9-12) Carbon Dioxide (CO2) Carbon Monoxide (CO) Particulate Matter (PM) Volatile Organic Compounds (VOCs) Ozone (O3) Bacteria Fungi School indoor air quality Positive pressure fresh air system PM2.5 Indoor environmental quality Ventilation The indoor-to-outdoor concentration ratios indicated that either outdoor sources or indoor+outdoor sources were the predominant contributors to PM in naturally ventilated classrooms. Meanwhile, PM levels in air-conditioned classrooms strongly depended on class activities. CO2 measurements showed that the air-conditioned classrooms had a low 0.4 per hour air change rate and total fungal counts also reached 800 CFU m-3. Analysis of gaseous organic compounds showed that the two most abundant were aliphatic and aromatic hydrocarbons, accounting for 60% by mass concentration. Interestingly, 2?ethyl?1?hexanol, a mucous membrane irritant, was detected in all study rooms. In one naturally ventilated classroom, we implemented a positive pressure fresh air system to mitigate in-class PM levels; it kept PM levels below 20 ?g m-3 throughout the class day. Students reported a 20-37% increase in satisfaction with the perceived indoor environmental quality and reported reduced rates in all symptoms of the sick building syndrome after implementing the positive pressure system.